Primary sources publish the law itself, i.e., the rules that local, state, and federal governments will enforce. Sources of primary law include ordinances, statutes, treaties, court decisions, administrative rules and regulations, administrative agency decisions, and executive orders and decrees. Example: U.S. Statutes at Large.

Secondary sources of law are materials that help find the law, or explain or comment on it, but are not "the law itself." Law review articles, treatises, legal encyclopedias, digests, and loose-leaf reports are secondary sources.

Official/ Unofficial

Official sources are those publications sanctioned by a government or court as the authoritative text of the law. Courts generally require citation to "official" sources of law. Example: United States Reports.

Unofficial sources are commercially published and often more timely. They are editorially enhanced to improve usefulness as a research tool. Increasingly, commercially published sources are being designated as the "official" texts to be cited to courts. Example: Supreme Court Reporter (West publication not designated as official).

Annotated/ Unannotated

Annotated sources publish the text of the law with augmenting information. The text of the law is primary material; the annotations are secondary material. Annotations can include case summaries, citations to cases interpreting the law, referrals to relevant periodical articles, legislative history, editorial notes, and analysis. Examples: Vernon's Annotate Missouri Statutes; United States Code Service.

Unannotated sources publish the bare text of the law. Example: United States Code.

Chronological Record/ Code:

Codes extract from the chronological record the laws and regulations still in force and bring them together in broad subject areas(e.g., civil code, criminal code, labor code, probate code).